1. Field of the Invention
The present invention relates to fluid pump outlet pressure regulation; and in particular to fluid pump outlet pressure regulation as a function of engine speed.
2. Description of the Related Art
It is known in the art relating to fluid pumps, such as engine oil pumps, to vary the pump output (displacement) as a function of pump outlet pressure in order to maintain a desired pump outlet pressure as the speed of the engine driving the pump is varied. Regulating the fluid pump outlet pressure can increase engine efficiency by reducing the volume of oil pumped at higher engine speeds with a resultant saving of energy.
Pressure-lubrication has been used with automotive internal combustion engines for many years. Typically, a single pressure relief valve is used to limit the maximum pressure developed by an oil pump. The relief pressure is usually set at a fairly high value, in order to assure that the engine receives adequate lubrication in all operating conditions from idle to maximum speed-load operation. Unfortunately, this causes the lubrication pump's energy consumption to be higher than would otherwise be ideal, because in many operating regimes, only a reduced volume and pressure of oil is required by the engine.
Other engine lubrication systems use an electrically operated pressure control valve. A solenoid opens and closes a ball valve to control the pressure within a pilot chamber for a pressure valve
It would be desirable to provide an engine lubrication system in which an engine is reliably protected with a pressure control valve, combined with the capability of maintaining an oil pressure within a predetermined pressure range so as to promote fuel economy improvement during all operating regimes.